The present disclosure relates to a liquid supply unit for supplying liquid stored in a liquid storage container to a liquid injection head and a liquid injection device to which the liquid supply unit is applied.
For example, in an ink jet printer, a liquid injection head for injecting a tiny amount of ink (liquid) to a print object is used. Ink is supplied to this liquid injection head from an ink cartridge (liquid storage container) storing the ink through a predetermined supply passage. Conventionally, a liquid injection device is known in which a liquid supply unit (valve unit) including a pressure chamber for setting a discharge hole of a liquid injection head to a negative pressure is arranged in a supply passage in the case of supplying ink from an ink cartridge to the liquid injection head by a water head difference. By disposing the liquid supply unit for generating the negative pressure, unlimited dripping of the ink from the discharge hole is suppressed even if the ink is supplied by the water head difference.
In the liquid injection device as described above, the ink is supplied to the liquid injection head via the pressure chamber for generating the negative pressure. Accordingly, a predetermined amount of the ink needs to be initially filled into the pressure chamber, such as during initial use and after maintenance. At this time, air in the pressure chamber needs to be vented. Further, the ink stored in the pressure chamber may generate air bubbles due to heating associated with the operation of the liquid injection device. Also in this case, the air in the pressure chamber needs to be vented.